Monoclonal Antibody-Based Immunosensor for the Electrochemical Detection of Chlortoluron Herbicide in Groundwaters

Chlortoluron (3-(3-chloro-p-tolyl)-1,1-dimethyl urea) is an herbicide widely used in substitution to isoproturon to control grass weed in wheat and barley crops. Chlortoluron has been detected in groundwaters for more than 20 years; and dramatic increases in concentrations are observed after intense rain outbreaks. In this context; we developed an immunosensor for the determination of chlortoluron based on competitive binding of specific monoclonal antibodies on chlortoluron and immobilized biotinylated chlortoluron; followed by electrochemical detection on screen-printed carbon electrodes. The optimized immunosensor exhibited a logarithmic response in the range 0.01-10 µg·L-1; with a calculated detection limit (LOD) of 22.4 ng·L-1; which is below the maximum levels allowed by the legislation (0.1 µg·L-1). The immunosensor was used for the determination of chlortoluron in natural groundwaters, showing the absence of matrix effects.

Fabrication of a Magnetic Fluorinated Covalent Organic Framework for the Selective Capture of Benzoylurea Insecticide Residue in Beverages

Efficient capture of benzoylurea insecticide (BU) residue in food is a vital procedure for food safe monitoring. Herein, a core-shell structured magnetic fluorinated covalent organic framework with good magnetic responsiveness and abundant fluorine affinity sites was successfully synthesized, suitable for magnetic solid-phase extraction (MSPE) of BUs. Using a room-temperature synthesis strategy, the magnetic fluorinated covalent organic framework was fabricated by in situ polymerization of 1,3,5-tris(4-aminophenyl) triazine (TAPT) and 2,3,5,6-tetrafluoroterephthaldehyde (TFTA) on the surface of carboxylated Fe₃O₄ nanoparticles. The competitive adsorption experiment and molecular simulation verified that this magnetic fluorinated covalent organic framework possesses favorable adsorption affinity for BUs. This magnetic fluorinated covalent organic framework could be easily regenerated and reused at least eight times with no reduction of enrichment performance. Combining this magnetic fluorinated covalent organic framework-based MSPE with high-performance liquid chromatography-tandem mass spectrometry, a novel sensitive method for the analysis of BUs was developed. In yellow wine and fruit juice samples, good linear correlations were obtained for BUs in the range of 10-2000 and 20-4000 ng·L^-1, respectively. The limit of quantitation of the BUs ranged from 1.4 to 13.3 ng·L^-1 in the two beverage matrices. Desirable precision was achieved, with intraday and interday relative standard deviations lower than 11%.

Electrochemistry-coupled to liquid chromatography-mass spectrometry-density functional theory as a new tool to mimic the environmental degradation of selected phenylurea herbicides

In vitro and in vivo experimental models, mainly based on cell cultures, animals, healthy humans and clinical trials, are useful approaches for identifying the main metabolic pathways. However, time, cost, and matrix complexity often hinder the success of these methods. In this study, we propose an alternative non-enzymatic method, using electrochemistry (EC) coupled to liquid chromatography (LC) - high resolution mass spectrometry (HRMS) - DFT theoretical calculations (EC/LC-MS/DFT) for the mimicry/simulation of the environmental degradation of phenylurea herbicides, and for the mechanism elucidation of this class of herbicides. Fenuron, monuron, isoproturon, linuron, monolinuron, metoxuron and chlortoluron were selected as relevant model compounds. The intended compounds are oxidized by EC, separated by LC and detected using electrospray ionization HRMS. The main oxidation products were hydroxylated compounds obtained by substitution and addition reactions. Unstable quinone imines/methines, rarely observed by conventional methods, have been identified during the oxidative degradation of phenylurea herbicides for the first time in this study. Some were directly observed and the others were trapped by glutathione GSH. Reactions such as hydrolytic substitutions (-Cl/+OH and -C₃H₇/+OH and -CH₃/+OH and -OCH₃/+OH), aromatic hydroxylation, alkyl carbon hydroxylation, dehydrochlorination/dehydromethylation/dehydromethoxylation and conjugation have been successfully mimicked. The obtained results, supported by theoretical calculations, are useful for simulating/understanding and predicting the oxidative degradation pathways of pesticides in the environment.

Dissipation kinetics and consumer risk assessment of novaluron + lambda-cyhalothrin co-formulation in cabbage

Cabbage, one of the most popular vegetables in the world is infested by several insect-pests and diseases. Novaluron, a chitin synthesis inhibitor and lambda-cyhalothrin, a synthetic pyrethroid group insecticide are used to manage insect-pests on cabbage. The dissipation kinetics and risk assessment of combination formulation (novaluron 9.45% + lambda-cyhalothrin 1.9%) with different modes of action has not yet been investigated in cabbage. Multi-location supervised field trials were therefore, conducted in different agro-climatic regions of India for safety evaluation of the combination product. The co-formulation at the recommended (novaluron 750 g a.i. ha^-1 + lambda-cyhalothrin 750 g a.i. ha^-1) and double the recommended (novaluron 1500 g a.i. ha^-1 + lambda-cyhalothrin 1500 g a.i. ha^-1) dose was sprayed on the cabbage crop. The samples were extracted and cleaned up using a modified QuEChERS method, and the residues analyzed by GC-ECD and GC-MS. The half-life (t_1/2) varied between 1.77 and 2.51 and 2.00-3.38 days for novaluron and 1.36-2.24 and 1.69-3.82 days for lambda-cyhalothrin in cabbage at respective doses. The Food Safety and Standards Authority of India (FSSAI) has set the MRL of 0.7 mg kg^-1 for novaluron at PHI of 5 days, and no MRL is set for lambda-cyhalothrin in cabbage. On the basis of OECD MRL calculator, the MRLs of 0.6 and 1.5 mg kg^-1 for novaluron and lambda-cyhalothrin, respectively were calculated at the respective doses at PHI of 3 days. Hazard quotient (HQ) <1, theoretical maximum daily intake (TMDI) < acceptable daily intake (ADI) and < maximum permissible intake (MPI), percent acute hazard index (% aHI) <1, and percent chronic hazard index (% cHI) <1 for both novaluron and lambda-cyhalothrin suggested that the combination formulation is safe and will not pose any dietary risk to the consumers. The study will be helpful to conduct risk assessment of other pesticides/combination pesticides on food crops on which their MRLs have not yet been fixed.

Sensitive simultaneous voltammetric determination of the herbicides diuron and isoproturon at a platinum/chitosan bio-based sensing platform

Phenylurea herbicides are persistent contaminants, which leads their transport to the surface and ground waters, affecting human and aquatic organisms. Different analytical methods have been reported for the detection of phenylureas; however, several of them are expensive, time-consuming, and require complex pretreatment steps. Here, we show a simple method for the simultaneous electrochemical determination of two phenylurea herbicides by differential pulse adsorptive stripping voltammetry (DPAdSV) using a modified platinum/chitosan electrode. The one-step synthesized platinum/chitosan PtNPs/CS was successfully characterized by TEM, XRPD, and FT-IR, and applied through the sensing platform designated as PtNPs/CS/GCE. This bio-based modified electrode is proposed for the first time for the individual and/or simultaneous electrochemical detection of the phenylurea herbicides diuron and isoproturon compounds extensively used worldwide that present a very similar chemical structure. Electrochemical and interfacial characteristics of the modified electrode were evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was found that the oxidation mechanism of diuron and isoproturon occurs in two different pathways, with a peak-to-peak definition of ca. 0.15 V. Under differential pulse adsorptive stripping voltammetry (DPAdSV) optimized conditions, the limit of detection (LOD) was estimated as 7 μg L^-1 for isoproturon and 20 μg L^-1 for diuron (E_d = +0.8 V; t_d = 100 s). The proposed method was successfully applied to the determination of both analytes in river water samples, at three different levels, with a recovery range of 90-110%. The employment of the bio-based sensing platform PtNPs/CS/GCE allows a novel and easy analytical method to the multi-component phenylurea herbicides detection.

Determination of Isoproturon in Environmental Samples using the QuEChERS Extraction-Spectrofluorimetric Method

An accurate and sensitive method has been developed for determination of the herbicide isoproturon using the Quick Easy Cheap Effective Rugged Safe (QuEChERS) extraction-spectrofluorimetric technique. The method involves the reaction of 2-cyanoacetamide with isoproturon in basic medium (NH₃ ; 15 mol/L). The resulting fluorescent product was found to show maximum emission at 378 nm and maximum excitation at 333 nm. Fluorescence intensity under the influence of different parameters was investigated. The linear range of analyte concentrations was found to be 0.5 to 15 µg/mL, with a limit of detection of 0.144 µg/mL, a limit of quantification of 0.437 µg/mL (signal to noise ratio = 3), and a regression coefficient of 0.9991, under optimized conditions. The proposed method was effectively applied for determination of isoproturon in different matrices; the percentage of recovery varied from 85.00 ± 1.2% to 96.00 ± 0.5%. The method was also applied for residue analysis of isoproturon in real soil samples collected from a pilot field. For extraction of isoproturon, the QuEChERS extraction approach was used, and the average residue in the soil samples was found to be 0.81 ± 0.07 µg/g. To show the potential of this approach, our results were compared with those of other methods reported in the literature. Environ Toxicol Chem 2019;38:2614-2620. © 2019 SETAC.

Dissipation of mecoprop-P, isoproturon, bentazon and S-metolachlor in heavy metal contaminated acidic and calcareous soil before and after EDTA-based remediation

The ability of contaminated farmland soils reclaimed by remediation to dissipate pesticides and thus to mitigate their unwanted environmental effects, i.e., leaching and run-off, was studied. Novel EDTA-based soil washing technology (EDTA and process waters recycling; no toxic emissions) removed 79 and 73% of Pb from acidic and calcareous soil with 740 and 2179 mg kg^-1 Pb, respectively. The dissipation kinetics of four herbicides: mecoprop-P, isoproturon, bentazon and S-metolachlor was investigated under field conditions in beds with maize (Zea mays) and barley (Hordeum vulgare). The biphasic First-Order Multi-Compartment (FOMC) model was used to fit experimental data and calculate the herbicides' half-life (DT₅₀) in soil. Remediation significantly (up to 64%) decreased dehydrogenase activity assessed as a marker of soil microbial activity and prolonged the DT₅₀ of herbicides in acidic soils from 16% (isoproturon) to 111% (S-metachlor). Remediation had a less significant effect on herbicide dissipation in calcareous soils; i.e., mecoprop-P DT₅₀ increased by 3%, while isoproturon and S-metachlor DT₅₀ decreased by 29%. Overall, the dissipation from remediated soils was faster than the average DT₅₀ of tested herbicides published in the Pesticides Properties DataBase. Results demonstrate that EDTA-based remediation of the studied soils does not pose any threat of extended herbicide persistence.

Biodegrading Two Pesticide Residues in Paddy Plants and the Environment by a Genetically Engineered Approach

Accumulating pesticide (and herbicide) residues in soils have become a serious environmental problem. This study focused on identifying the removal of two widely used pesticides, isoproturon (IPU) and acetochlor (ACT), by a genetically developed paddy (or rice) plant overexpressing an uncharacterized glycosyltransferase (IRGT1). IRGT1 conferred plant resistance to isoproturon-acetochlor, which was manifested by attenuated cellular injury and alleviated toxicity of rice under isoproturon-acetochlor stress. A short-term study showed that IRGT1-transformed lines removed 33.3-48.3% of isoproturon and 39.8-53.5% of acetochlor from the growth medium, with only 59.5-72.1 and 58.9-70.4% of the isoproturon and acetochlor remaining in the plants compared with the levels in untransformed rice. This phenotype was confirmed by IRGT1-expression in yeast ( Pichia pastoris) which grew better and contained less isoproturon-acetochlor than the control cells. A long-term study showed that isoproturon-acetochlor concentrations at all developmental stages were significantly lower in the transformed rice, which contain only 59.3-69.2% (isoproturon) and 51.7-57.4% (acetochlor) of the levels in wild type. In contrast, UPLC-Q-TOF-MS/MS analysis revealed that more isoproturon-acetochlor metabolites were detected in the transformed rice. Sixteen metabolites of isoproturon and 19 metabolites of acetochlor were characterized in rice for Phase I reactions, and 9 isoproturon and 13 acetochlor conjugates were characterized for Phase II reactions in rice; of these, 7 isoproturon and 6 acetochlor metabolites and conjugates were reported in plants for the first time.

Previous degradation study of two herbicides to simulate their fate in a sandy loam soil: Effect of the temperature and the organic amendments

A laboratory study was designed to assess the following: i) the degradation kinetics of chlorotoluron and flufenacet at two different temperatures, 6 °C and 16 °C, in an unamended agricultural soil and one amended with spent mushroom substrate (SMS) and green compost (GC), and ii) the formation of the main metabolites of both herbicides with potential risk for water pollution over degradation time. The aim was to determine the dependence of these herbicide degradations on temperature (Q₁₀ factor) using kinetic parameters, which is essential information for the later simulation of herbicide environmental fate with FOCUS models. SMS and GC were applied in situ to the natural soil as organic amendments at rates of 140 or 85 t residue ha^-1, respectively. Unamended and amended soils were taken from the 0-10 cm topsoil of experimental plots (three replicates/treatment) located on an agricultural farm. Samples of soil + herbicides were incubated at 6 °C or 16 °C under laboratory conditions. The degradation curves of chlorotoluron and flufenacet were fitted to single first-order and first-order multicompartment kinetic models, respectively. The flufenacet degradation, the more hydrophobic herbicide, was slower than that of chlorotoluron in all the treatments. The application of the organic amendments to soil increased the half-lives (DT₅₀) for both herbicides incubated at 6 °C (1.3-1.9 times) and 16 °C (1.4-1.9 times) due to their higher sorption and lower bioavailability for degradation in amended soils. The herbicides recorded a faster degradation at 16 °C than at 6 °C (Q₁₀ = 1.9-2.8) due to the increased microbial biomass and/or activity with temperature. The metabolites desmethyl chlorotoluron, flufenacet ESA and flufenacet OA were detected in all the soil treatments at both incubation temperatures. The determination of Q₁₀ factors in amended soils is very valuable for generating accurate input data for pesticide fate models such as FOCUS in order to improve the evaluation of the leaching of herbicides and their transformation products, which is a relevant goal to maintain the sustainability of agricultural systems.

Three approaches to minimize matrix effects in residue analysis of multiclass pesticides in dried complex matrices using gas chromatography tandem mass spectrometry

This paper discusses one of the major concerns in pesticide residue analysis: the matrix effect related to gas chromatography (GC), which can adversely affect quantification. In this study, a comparison of approaches for dealing with the matrix effect was investigated for 236 pesticides in complex matrices, including dried herbs (Centaurea cyanus L., Matricaria chamomilla L., Thymus vulgaris L.) and dried fruit (currants, chokeberry), using a modified QuEChERS method and GC-MS/MS analysis. Three approaches were evaluated: (i) using matrix-matched calibration, (ii) adding a mixture of analyte protectants (APs) to every extract or (iii) injection prior to GC-MS/MS analysis. Finally, minimization of the matrix effect to the acceptable levels of -20 to 20% for over 80% of investigated pesticides was found when APs mixture was injected at the beginning of the sequence. In this approach, the matrix effects were significantly weaker for some pesticides than when matrix-matched calibration was used.

Residue investigation of some phenylureas and tebuthiuron herbicides in vegetables by ultra-performance liquid chromatography coupled with integrated selective accelerated solvent extraction-clean up in situ

BACKGROUND

Some trace amounts of urea herbicide residues can be transferred to humans via the food chain, thereby being potentially harmful to human health. The development of a robust analytical methodology for effective sample preparation and simultaneous determination of herbicide residues in vegetable samples is required for achieving food safety.

RESULTS

The diuron-molecularly imprinted polymers (MIPs) synthesized have excellent affinity and high selectivity to phenylureas (monolinuron, isoproturon, diuron and linuron) and tebuthiuron. A novel automated procedure with better selectivity for vegetable sample treatment was developed by integrated matrix solid-phase dispersion-accelerated solvent extraction clean-up in situ. Five herbicides can be baseline separated with runtime down to 5 min by ultra-performance liquid chromatography, and good linearity was obtained with a correlation coefficient (r) of 0.9999. The limit of quantification of the method was in the range of 0.8-2.3 µg kg^-1 . Diuron residue in cherry tomato sample was found to be 40 µg kg^-1 .

CONCLUSION

The developed method has satisfactory selectivity, good linearity, high sensitivity and accuracy as well as speediness, and can ensure rapid selective extraction and sensitive multi-residue analysis at low microgram per kilogram levels of the herbicides in vegetable food. © 2018 Society of Chemical Industry.

Characterization of adsorption and desorption of lawn herbicide siduron in heavy metal contaminated soils

Siduron is a widely used herbicide in urban lawn and has been frequently detected in urban and suburban surface water. However, characteristics of its environmental behavior in soil are seldom reported. The combined pollution of heavy metals, especially for Cu, Pb, Cd, Zn and siduron would be common because of the widely existence of heavy metal pollution in urban soils. In this study, four soils with similar physicochemical properties but different levels of preexisting heavy metals were selected to investigate the adsorption and successive desorption of siduron using batch experiments. The results revealed a low sorption of siduron to all the tested soils. The organic carbon normalized distribution coefficient (K_oc) of siduron in the studied soils ranged from 117 to 137 L kg^-1 and was not significantly correlated to heavy metal levels. No apparent desorption hysteresis was observed with the hysteresis index (HI) ranging from 0.921 to 1.11. More than 50% of the sorbed siduron was readily released into soil solution. Results suggested that siduron was highly mobile and bioavailable in the studied soils. Significant correlation was found between adsorption/desorption parameters and soil organic carbon (SOC) in four soils. soil organic matter was thus considered as the dominant factor determining the adsorption and desorption of siduron in soils. Different from most of reported studies conducted by laboratory-amended soils, the influence of preexisting heavy metals on the adsorption-desorption of siduron was not significant in this work.

Ecological risk evaluation of combined pollution of herbicide siduron and heavy metals in soils

Combined pollution of agrichemicals and heavy metals in urban lawn soils were commonly observed throughout the world, and the co-existed two chemicals could interact with each other both in environment behavior and toxic effect. However, little has been reported on the ecological risk of their combined pollution, especially in field due to lack of systematic methodology. In this study, four soils (C, N1, N2, N3) from two public parks in Beijing, China, with similar properties but contrasting heavy metal contaminated level were chosen to assess the ecological risks of co-existed herbicide siduron and heavy metals. Environmental behaviors of siduron in studied soils were investigated with batch experiments in lab, based on which the environmental exposure level of siduron was simulated with HYDRUS-1D. Results suggested that soil organic matter (SOM) rather than the co-existed heavy metals was the dominant factor affecting the fate and the accumulation of siduron in soils. Soil N2 with the highest SOM, showed the strongest tendency to retain siduron among the studied soils. Significant joint effect of siduron and heavy metals on cucumber root elongation was observed through lab experiments. Thus, the joint toxicity of siduron and heavy metals were calculated based on single toxicology data of them using independent action (IA) and concentration addition (CA) model. Then, the predicted no effect concentration (PNEC_soil) of siduron was calculated with equilibrium partitioning method and extrapolation techniques. The PNEC_soil of siduron was the lowest in heaviest heavy metal contaminated soil N3. The risk characterization ratios (RCR) of siduron in four soils were all >1. The highest RCR of siduron in soil N3 suggested that it was the joint toxicity of siduron and heavy metals to organisms determining the ecological risks of siduron in combined polluted soils.

Inoculation of soil with an Isoproturon degrading microbial community reduced the pool of "real non-extractable" Isoproturon residues

During pesticides degradation, biogenic non-extractable residues ("apparent NER") may not share the same environmental fate and risks with the "real NER" that are bound to soil matrix. It is not clear how microbial community (MC) inoculation for pesticides degradation would influence the NER composition. To investigate degradation efficiency of pesticides Isoproturon (IPU) and NER composition following MC inoculation, clay particles harboring MC that contains the IPU degrading strain, Sphingomonas sp., were inoculated into soil receiving ¹⁴C-labeled IPU addition. Mineralization of IPU was greatly enhanced with MC inoculation that averagely 55.9% of the applied ¹⁴C-IPU was consumed up into ¹⁴CO₂ during 46 days soil incubation. Isoproturon degradation was more thorough with MC than that in the control: much less amount of metabolic products (4.6% of applied IPU) and NER (35.4%) formed in MC treatment, while the percentages were respectively 30.3% for metabolites and 49.8% for NER in the control. Composition of NER shifted with MC inoculation, that relatively larger amount of IPU was incorporated into the biogenic "apparent NER" in comparison with "real NER". Besides its well-recognized role on enhancing mineralization, MC inoculation with clay particles benefits soil pesticides remediation in term of reducing "real NER" formation, which has been previously underestimated.

Persistence of chlorfluazuron in cabbage under different agro-climatic conditions of India and its risk assessment

A multilocational field trial was conducted at 4 locations in India-Rajasthan, Gujarat, Madhya Pradesh, and West Bengal-to determine the persistence in cabbage of chlorfluazuron applied twice at 75 and 150 g active ingredient ha^-1 . Cabbage head samples were collected from each replicated plot on 0 (2 h after spraying), 1, 3, 5, 7, 10, and 15 d after final insecticide application, including an untreated control. Chlorfluazuron residue in cabbage and field soil was estimated by high-performance liquid chromatography using a photo diode array detector. The limit of determination and limit of quantification of the method were recorded as 0.05 and 0.10 μg g^-1 , respectively. Results revealed that chlorfluazuron dissipated linearly with progress of time, following first-order kinetics. The mean (± standard deviation) half-life value of chlorfluazuron in cabbage was found to be 7.18 ± 0.71 d, considering different locations and treatments. The residue was below the level of quantification in the harvested cabbage and soil samples. Harvesting cabbage in the experimental location, at least on day 7, after 2 applications of chlorfluazuron at the recommended dose, may not pose any ill effect for Indian adults. Environ Toxicol Chem 2017;36:3028-3033. © 2017 SETAC.

Transformation products elucidation of forchlorfenuron in postharvest kiwifruit by time-of-flight mass spectrometry

Forchlorfenuron (1-(2-chloro-4-pyridyl)-3-phenylurea, FCF) is a plant growth regulator, being extensively used for increasing kiwifruit size. The toxicological properties of its may persist in their transformation products (TPs) or even higher toxicity than FCF. TPs elucidation of FCF in postharvest kiwifruit (Actinidia chinensis, Chinese gooseberry) by the liquid chromatography ionization hybrid ion trap and time-of-flight mass spectrometry (LC-ESI-IT-TOF/MS) in positive mode was the objective of the present study. Fifteen days after full bloom, kiwifruits were dipped for 5s with high dosage FCF solution (60 mg/L), so that sufficient peaks could be detected. The chemical structure of unknown TPs was analyzed in combination of functions of LCMS-IT-TOF, such as high-accurate MSⁿ, formula predictor, metabolite structural analysis software MetID Solution, profiling solution metabolomics software, and neutral loss, characteristic isotopic patterns of chlorine, the fragmentation pattern and retention time of standard substances, nitrogen rule, chemical components of kiwifruit. Total 17 TPs were detected via comparisons of their accurate MSⁿ data of commercial analytical standards and synthesized standards with high purity, such as 4-amino-2-chloropyridine, phenylurea, 2-hydroxy-FCF, 1-(2-chloro-6-((3, 4, 5-trihydroxy-6-(hydroxymethyl) tetrahydro-2H-pyran-2-yl) oxy) pyridin-4-yl)-3-phenylurea, 1, 3-bis (2-chloropyridin-4-yl) urea, 1,3-diphenylurea, 1-(2-chloropyridin-4-yl)urea, FCF-2-O-β-D-glucoside, and so on. The major transformation pathways of FCF in kiwifruit were biochemical and photochemical cleavage pathway. The experimental results indicate that LCMS-IT-TOF is powerful and effective tool for identification of FCF TPs.

Herbicide micropollutants in surface, ground and drinking waters within and near the area of Zagreb, Croatia

The frequency and mass concentrations of 13 herbicide micropollutants (triazines, phenylureas, chloroacetanilides and trifluralin) were investigated during 2014 in surface, ground and drinking waters in the area of the city of Zagreb and its suburbs. Herbicide compounds were accumulated from water by solid-phase extraction using either octadecylsilica or styrene-divinylbenzene sorbent cartridges and analysed either by high-performance liquid chromatography with UV-diode array detector or gas chromatography with mass spectrometric detection. Atrazine was the most frequently detected herbicide in drinking (84 % of samples) and ground (61 % of samples) waters in mass concentrations of 5 to 68 ng L^-1. It was followed by metolachlor and terbuthylazine, the former being detected in 54 % of drinking (up to 15 ng L^-1) and 23 % of ground (up to 100 ng L^-1) waters, and the latter in 45 % of drinking (up to 20 ng L^-1) and 26 % of ground (up to 25 ng L^-1) water samples. Acetochlor was the fourth most abundant herbicide in drinking waters, detected in 32 % of samples. Its mass concentrations of 107 to 117 ng L^-1 in three tap water samples were the highest of all herbicides measured in the drinking waters. The most frequently (62 % of samples) and highly (up to 887 ng L^-1) detected herbicide in surface waters was metolachlor, followed by terbuthylazine detected in 49 % of samples in mass concentrations of up to 690 ng L^-1, and atrazine detected in 30 % of samples in mass concentrations of up to 18 ng L^-1. The seasonal variations in herbicide concentrations in surface waters were observed for terbuthylazine, metolachlor, acetochlor, chlortoluron and isoproturon with the highest concentrations measured from April to August.

Methods comparison, transport and distribution of polar herbicides in the Baltic Sea

Two LC-MS/MS methods including different sample preparation and quantitative processes showed a good agreement for analysis of the herbicides MCPA, mecoprop, isoproturon, bentazon and chloridazon, and the metabolite chloridazon-methyl-desphenyl (CMD) in estuarine waters. Due to different sensitivity of the methods only one could be used to analyze marine samples. The transport of these compounds to the Baltic Sea via ten German estuaries and their distribution between coastal water and sediments was studied. The results showed that all selected compounds can be transported to the Baltic Sea (0.9-747ng/L). Chloridazon, bentazon, isoproturon and CMD were detected (0.9-8.9ng/L) in the coastal waters and chloridazon and isorproturon in the sediments (5-136pg/g d.w.). Levels of contaminants in the sediments could be influenced by the total organic carbon content. Concentrations observed in the Baltic Sea are most likely not high enough to cause acute effects, but long term effect studies are strongly recommended.

Chronic and acute risk assessment of human exposed to novaluron-bifenthrin mixture in cabbage

Based on the dissipation and residual level in cabbage determined by gas chromatography coupled with an electron capture detector (GC-ECD), chronic and acute risk assessments of the novaluron and bifenthrin were investigated. At different spiked levels, mean recoveries were between 81 and 108 % with relative standard deviations (RSDs) from 1.1 to 6.8 %. The limit of quantification (LOQ) was 0.01 mg kg(-1), and good linearity with correlation coefficient (>0.9997) were obtained. The half-lives of novaluron and bifenthrin in cabbage were in the range of 3.2~10 days. Based on the consumption data in China, the risk quotients (RQs) of novaluron and bifenthrin were all below 100 %. The chronic and acute risk of novaluron in cabbage was relatively low, while bifenthrin exerts higher acute risk to humans than chronic risk. The obtained results indicated that the use of novaluron-bifenthrin mixture does not seem to pose any chronic or acute risk to humans even if cabbages are consumed at high application dosages and short preharvest interval (PHI).

Properties of biochar-amended soils and their sorption of imidacloprid, isoproturon, and atrazine

Biochars produced from rice straw, wheat straw and swine manure at 300, 450 and 600°C were added to soil at 1, 5, 10, or 20% levels to determine whether they would predictably reduce the pore water concentration of imidacloprid, isoproturon, and atrazine. The sorption capacity of the mixtures increased with increasing biochar amounts. The enhanced sorption capacity could be attributed to the increased organic carbon (OC) content and surface area (SA) as well as the decreased hydrophobicity. Biochar dominated the overall sorption when its content was above 5%. The OC contents of the mixtures with 10% and 20% biochar were generally lower than the predicted values. This implies possible interaction between soil components and biochar and/or the effect of biochar oxidation. For soils amended with biochars produced at 300°C, the N2 SA (N2-SA) values were underestimated. The predicted CO2 SA (CO2-SA) values of the mixtures at the biochar content of 10% and 20% were generally higher than the experimental values. Sorption of imidacloprid to the soils amended with biochar at 10% and 20% levels, excluding the soils amended with rice (SR300) and wheat (SW300) straw-derived biochar produced at 300°C, was lower than the predicted value. For SR300 and SW300, the intrinsic sorption capacity of biochar was enhanced by 1.3-5.6 times, depending on the biochar, solute concentration, and biochar dose. This study indicates that biochars would be helpful to stabilize the soil contaminated with imidacloprid, isoproturon, and atrazine, but the sorption capacity of the mixtures could exceed or fall short of predicted values without assuming a cross-effect between soil and biochar.

Predicting isoproturon long-term mineralization from short-term experiment: Can this be a suitable approach?

A worldwide used pesticide - isoproturon (IPU) - was selected to test whether short-term experiments can be used to predict long-term mineralization of IPU in soil. IPU-mineralization was measured for 39 and 265 days in four different agricultural soils with a low mineralization dynamic. Additionally, in one soil IPU dissipation, formation and dissipation of metabolites, formation of non-extractable residues (NER) and (14)C-microbial biomass from (14)C-IPU were monitored for 39 and 265 days. The data from short-term and long-term experiments were used for model fitting. The long-term dynamics of IPU mineralization were considerably overestimated by the short-term experiments in two soils with neutral pH, while in two other soils with low pH and lower mineralization, the long-term mineralization of IPU could be sufficiently predicted. Additional investigations in one of the soils with neutral pH showed that dissipation of IPU and metabolites could be correctly predicted by the short-term experiment. However, the formation of NER and (14)C-microbial biomass were remarkably overestimated by the short-term experiment. Further, it could be shown that the released NER and (14)C-microbial biomass were the main contributors of (14)CO2 formation at later incubation stages. Taken together, our results indicate that in soils with neutral pH short-term experiments were inadequate to predict the long-term mineralization of IPU.

Fatty Acid Methyl Ester (FAME) Succession in Different Substrates as Affected by the Co-Application of Three Pesticides

Introduction

In intensive agriculture areas the use of pesticides can alter soil properties and microbial community structure with the risk of reducing soil quality.

Materials and Methods

In this study the fatty acid methyl esters (FAMEs) evolution has been studied in a factorial lab experiment combining five substrates (a soil, two aged composts and their mixtures) treated with a co-application of three pesticides (azoxystrobin, chlorotoluron and epoxiconazole), with two extraction methods, and two incubation times (0 and 58 days). FAMEs extraction followed the microbial identification system (MIDI) and ester-linked method (EL).

Results and Discussion

The pesticides showed high persistence, as revealed by half-life (t_1/2) values ranging from 168 to 298 days, which confirms their recalcitrance to degradation. However, t_1/2 values were affected by substrate and compost age down to 8 days for chlorotoluron in S and up to 453 days for epoxiconazole in 12M. Fifty-six FAMEs were detected. Analysis of variance (ANOVA) showed that the EL method detected a higher number of FAMEs and unique FAMEs than the MIDI one, whereas principal component analysis (PCA) highlighted that the monosaturated 18:1ω9c and cyclopropane 19:0ω10c/19ω6 were the most significant FAMEs grouping by extraction method. The cyclopropyl to monoenoic acids ratio evidenced higher stress conditions when pesticides were applied to compost and compost+soil than solely soil, as well as with final time.

Conclusion

Overall, FAMEs profiles showed the importance of the extraction method for both substrate and incubation time, the t_1/2 values highlighted the effectiveness of solely soil and the less mature compost in reducing the persistence of pesticides.

A validated LC-MS/MS method of total and unbound lenvatinib quantification in human serum for protein binding studies by equilibrium dialysis

A sensitive method for the determination of total and unbound lenvatinib (Lenvima™), a novel tyrosine kinase inhibitor, in human serum was developed for protein binding studies using an equilibrium dialysis and liquid chromatography with tandem mass spectrometry. Serum samples (0.8 mL) were dialyzed against phosphate buffered saline (PBS) in dialyzer for 18 h at 37 °C to obtain dialysate and serum for unbound and total lenvatinib, respectively. After extraction by organic solvent, separation was achieved on a Symmetry Shield RP8 column with isocratic elution of 2 mM ammonium acetate (pH 4.0)-acetonitrile (3:2, v/v) at the flow rate of 0.2 mL/min. Detection was performed using API4000 with multiple reaction monitoring mode using positive electrospray ionization. The standard curve ranged from 0.0400 to 16.0 ng/mL and 0.0800 to 400 ng/mL as lenvatinib free base in PBS and serum, respectively. Accuracy and precision in the intra- and inter-batch reproducibility study were within the acceptance criteria. Various stability assessments including bench-top, freeze/thaw, processed samples, and frozen stability confirmed that lenvatinib was stable in serum and PBS. Application to in vivo protein binding studies in clinical studies was successfully performed and results showed that lenvatinib was highly protein bound in serum.

Dispersive micro-solid-phase extraction of herbicides in vegetable oil with metal-organic framework MIL-101

Dispersive microsolid-phase extraction based on metal-organic framework has been developed and applied to the extraction of triazine and phenylurea herbicides in vegetable oils in this work. The herbicides were directly extracted with MIL-101 from diluted vegetables oils without any further cleanup. The separation and determination of herbicides were carried out on high performance liquid chromatography. The effects of experimental parameters, including volume ratio of n-hexane to oil sample, mass of MIL-101, extraction time, centrifugation time, eluting solvent, and elution time were investigated. The Student's t test was applied to evaluate the selected experimental conditions. The limits of detection for the herbicides ranged from 0.585 to 1.04 μg/L. The recoveries of the herbicides ranged from 87.3 to 107%. Our results showed that the present method is rapid, simple, and effective for extracting herbicides in vegetable oils.

Photochemical transformation of phenylurea herbicides in surface waters: a model assessment of persistence, and implications for the possible generation of hazardous intermediates

This work models the phototransformation kinetics in surface waters of five phenylurea herbicides (diuron, fenuron, isoproturon, metoxuron and chlortoluron), for which important photochemical parameters are available in the literature (direct photolysis quantum yields and reaction rate constants with ·OH, CO3(-·) and the triplet states of chromophoric dissolved organic matter, (3)CDOM*). Model calculations suggest that isoproturon and metoxuron would be the least photochemically persistent and diuron the most persistent compound. Reactions with ·OH and (3)CDOM* would be the main phototransformation pathways for all compounds in the majority of environmental conditions. Reaction with CO3(-) could be important in waters with low dissolved organic carbon (DOC), while direct photolysis would be negligible for fenuron, quite important for chlortoluron, and somewhat significant for the other compounds. The direct photolysis of metoxuron and diuron is known to increase toxicity, and such a photoreaction pathway would be enhanced at intermediate DOC values (1-4 mg C L(1)). The reaction between phenylureas and ·OH is known to produce toxic intermediates, differently from (3)CDOM*. Therefore, the shift of reactivity from ·OH to (3)CDOM* with increasing DOC could reduce the environmental impact of photochemical transformation.

Modeling the effect of soil structure on water flow and isoproturon dynamics in an agricultural field receiving repeated urban waste compost application

Transport processes in soils are strongly affected by heterogeneity of soil hydraulic properties. Tillage practices and compost amendments can modify soil structure and create heterogeneity at the local scale within agricultural fields. The long-term field experiment QualiAgro (INRA-Veolia partnership 1998-2013) explores the impact of heterogeneity in soil structure created by tillage practices and compost application on transport processes. A modeling study was performed to evaluate how the presence of heterogeneity due to soil tillage and compost application affects water flow and pesticide dynamics in soil during a long-term period. The study was done on a plot receiving a co-compost of green wastes and sewage sludge (SGW) applied once every 2 years since 1998. The plot was cultivated with a biannual rotation of winter wheat-maize (except 1 year of barley) and a four-furrow moldboard plow was used for tillage. In each plot, wick lysimeter outflow and TDR probe data were collected at different depths from 2004, while tensiometer measurements were also conducted during 2007/2008. Isoproturon concentration was measured in lysimeter outflow since 2004. Detailed profile description was used to locate different soil structures in the profile, which was then implemented in the HYDRUS-2D model. Four zones were identified in the plowed layer: compacted clods with no visible macropores (Δ), non-compacted soil with visible macroporosity (Γ), interfurrows created by moldboard plowing containing crop residues and applied compost (IF), and the plow pan (PP) created by plowing repeatedly to the same depth. Isoproturon retention and degradation parameters were estimated from laboratory batch sorption and incubation experiments, respectively, for each structure independently. Water retention parameters were estimated from pressure plate laboratory measurements and hydraulic conductivity parameters were obtained from field tension infiltrometer experiments. Soil hydraulic properties were optimized on one calibration year (2007/08) using pressure head, water content and lysimeter outflow data, and then tested on the whole 2004/2010 period. Lysimeter outflow and water content dynamics in the soil profile were correctly described for the whole period (model efficiency coefficient: 0.99) after some correction of LAI estimates for wheat (2005/06) and barley (2006/07). Using laboratory-measured degradation rates and assuming degradation only in the liquid phase caused large overestimation of simulated isoproturon losses in lysimeter outflow. A proper order of magnitude of isoproturon losses was obtained after considering that degradation occurred in solid (sorbed) phase at a rate 75% of that in liquid phase. Isoproturon concentrations were found to be highly sensitive to degradation rates. Neither the laboratory-measured isoproturon fate parameters nor the independently-derived soil hydraulic parameters could describe the actual multiannual field dynamics of water and isoproturon without calibration. However, once calibrated on a limited period of time (9 months), HYDRUS-2D was able to simulate the whole 6-year time series with good accuracy.

Determination of forchlorfenuron in fruits by solid phase or QuECHERS extraction and LC-UV or LC/MS/MS

Forchlorfenuron, N-(2-chloro-4-pyridinyl)-N'-phenylurea, is a plant growth regulator used to increase the size of kiwifruit, apples, table grapes, and peaches and to promote increased yields of potatoes, rice, and wheat. This study reports the comparison of the performances of two extraction methods [Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) and SPE] and two analytical methods (LC-UV and a LC/MS/MS) when determining forchlorfenuron in apples, kiwis, and grapes. Both extraction methods gave recoveries of forchlorfenuron from fruits >70%. The QuEChERS method was cheaper, safer, and less time-consuming than the SPE method and can be recommended for routine analysis. The LOQ was 2 and 10 microg/kg for the LC/MS/MS and LC-UV analysis, respectively. The LOD was 1 and 5 microg/kg for the LC/MS/MS and LC-UV analysis, respectively. The sensitivity of the LC-UV analysis was adequate to measure residue levels five times lower than the maximum residue limit (MRL) of the product. The QuEChERS and SPE methods were applied to monitoring the persistence of forchlorfenuron in field-treated kiwis, and it was found that the residual concentration was already much lower than the MRL 7 days after treatment.

Leaching potential of phenylurea herbicides in a calcareous soil: comparison of column elution and batch studies

The transfer of eleven phenylurea herbicides through soil columns was investigated in laboratory conditions in order to determine leaching properties in a calcareous soil. Elution curves with distilled water were plotted after herbicide application on the soil column. Phenylurea retention by the soil indicating interactions with soil can be classified as follows: fenuron < fluometron ≤ isoproturon = monuron < metoxuron < monolinuron < metobromuron < chlorotoluron < linuron = diuron < chlorbromuron. The number and nature of halogen atoms on the phenyl ring had an important influence on leaching. Retention was higher for molecules with higher number of halogen, and it was also higher for bromine than chlorine. Column elution experiments were compared to batch experiments from which the distribution coefficients K d were determined. According to Kendall correlation coefficients, parameter m/m 0 max from column experiments was relatively well linked to K d. In case of phenylurea, a linear relationship between K d and m/m 0 max was established.

Determination of picogram quantities of chlortoluron in soil samples by luminol-chitosan chemiluminescence system

Based on the enhancing effect of chitosan (CS) on luminol-dissolved oxygen chemiluminescence (CL) reaction, a flow injection (FI) luminol-CS CL system was established. It was found that the increase of CL intensity was proportional to the concentrations of CS ranging from 0.7 to 10.0 μmol l(-1). In the presence of chlortoluron (CTU), the CL intensity of luminol-CS system could be obviously inhibited and the decrements of CL intensity were linearly proportional to the logarithm of CTU concentrations ranging from 0.01 to 70.0 ng ml(-1), giving the limit of detection 3.0 pg ml(-1) (3σ). At a flow rate of 2.0 ml min(-1), the whole process including sampling and washing could be accomplished within 36 s, offering a sample throughput of 100 h(-1). The proposed FI-CL method was successfully applied to the determination of CTU in soil samples with recoveries ranging from 95.0 % to 105.3 % and the relative standard deviations (RSDs) of less than 4.0 %.

Influence of biochar on isoproturon partitioning and bioaccessibility in soil

The influence of biochar (5%) on the loss, partitioning and bioaccessibility of (14)C-isoproturon ((14)C-IPU) was evaluated. Results indicated that biochar had a dramatic effect upon (14)C-IPU partitioning: (14)C-IPU extractability (0.01 M CaCl2) in biochar-amended treatments was reduced to <2% while, (14)C-IPU extractability in biochar free treatments decreased with ageing from 90% to 40%. A partitioning model was constructed to derive an effective partition coefficient for biochar:water (KBW of 7.82 × 10(4) L kg(-1)). This was two orders of magnitude greater than the apparent Kfoc value of the soil organic carbon:water (631 L kg(-1)). (14)C-radiorespirometry assays indicated high competence of microorganisms to mineralise (14)C-IPU in the absence of biochar (40.3 ± 0.9%). Where biochar was present (14)C-IPU mineralisation never exceeded 2%. These results indicate reduced herbicide bioaccessibility. Increasing IPU application to ×10 its recommended dose was ineffective at redressing IPU sequestration and its low bioaccessibility.

Dissipation and residue of forchlorfenuron in citrus fruits

Field trials were carried out in three provinces of China to study the dissipation and residue of forchlorfenuron in citrus fruits. The results had shown that the degradation rate of forchlorfenuron in citrus fruits followed the first-order kinetics equation C = A∙eBt. The half-lives of forchlorfenuron were 15.8-23.0 days, the final residues of forchlorfenuron in pulp were all ≤0.002 mg/kg, and most of the residues were concentrated in the peel. The risk assessment revealed that no significant potential health risk would be induced by forchlorfenuron in citrus fruits. Therefore, it could be safe to apply forchlorfenuron in citrus fruits, and the results of this study could also be regarded as a reference to the setting of maximum residue limit for forchlorfenuron in citrus fruits in China.

Photocatalytic degradation of substituted phenylurea herbicides in aqueous semiconductor suspensions exposed to solar energy

The photocatalyzed degradation of the biocides chlorotoluron, diuron, fluometuron, isoproturon and linuron (substituted phenylurea herbicides) was investigated in aqueous suspensions of ZnO, TiO2, WO3, SnO2 and ZnS at pilot plant scale under natural sunlight. Comparison of the five catalysts showed that ZnO is the most effective for catalyzing the removal of all the compounds studied. The primary degradation of the herbicides followed a pseudo-first order kinetics. In our conditions, the time required for 90% degradation ranged from 23 to 47min for isoproturon and linuron, respectively, when using the tandem ZnO/Na2S2O8. Eight transformation products were identified by HPLC-MS(2) during the experiments, although at the end of the photoperiod (240min), their concentrations were below detection limits. Based on derivative identification, the proposed metabolic pathways would involve N-demethylation and N-demethoxylation of the N-methoxy-N-methyl substituted ureas and N-demethylation of the N,N-dimethylurea-substituted compounds.

Mapping field spatial distribution patterns of isoproturon-mineralizing activity over a three-year winter wheat/rape seed/barley rotation

The temporal and spatial variability of the activity of soil microorganisms able to mineralize the herbicide isoproturon (IPU) pesticide was investigated over a three-year long crop rotation between 2008 and 2010. Isoproturon mineralization was higher in 2008, when winter wheat was treated with this herbicide, than in 2009 and 2010, when rape seed and barley were treated with different herbicides. Under laboratory conditions, we showed that isoproturon mineralization was not promoted by sulfonylurea herbicide applied on barley crop in 2010. IPU mineralization was shown to be highly variable at the field scale in years 2009 and 2010. Principal component analyses and analyses of similarities revealed that soil pH and equivalent humidity, and to a lesser extent soil organic matter content and cation exchange capacity (CEC) were the main drivers of isoproturon-mineralizing activity variance. Using a rather simple model that yields the rate of isoproturon mineralization as a function of soil pH and equivalent humidity, we explained up to 85% of the variance observed. Mapping field-scale distribution of isoproturon mineralization over the three-year survey indicated higher variability in 2009 and in 2010 as compared to 2008, suggesting that isoproturon treatment applied to winter wheat promoted isoproturon mineralization activity and reduced its spatial variability. Field-scale distribution of isoproturon mineralization showed important similarity to the distribution of soil pH, equivalent humidity and to a lesser extent to soil organic matter and cation exchange capacity (CEC) thereby confirming our model.

Pesticide pressure and fish farming in barrage pond in Northeastern France. Part II: residues of 13 pesticides in water, sediments, edible fish and their relationships

Residues of pesticides in fish farming productions from barrage ponds are seldom studied in spite of increasing health questionings and environmental concerns. The purpose of this study is to establish the pesticide contamination profiles of sediments and edible fish from five ponds in Northeastern France. Multi-residues method and liquid chromatography-tandem mass spectrometry analysis were used to quantify 13 pesticides (azoxystrobin, carbendazim, clomazone, diflufenican, dimethachlor, fluroxypyr, iprodion, isoproturon, mesosulfuron-methyl, metazachlor, napropamid, quizalofop and thifensulfuron-methyl). Ten sediments and 143 muscles samples were analysed, corresponding to two successive fishing campaigns (first fishing date and second fishing date (P2), about 1 year later) on five sites (noted C-0, C-25, C-45, C-75 and C-85 to express the increasing gradient of crop area). Isoproturon was present in all sediments samples (1.8-56.4 μg/kg dry weight). During P2 period, carbendazim was quantified in the fish of site C-0 (0.09 ± 0.02, 0.2 ± 0.1 and 0.17 ± 0.06 μg/kg wet weight (ww) for roach, carp and perch, respectively). Metazachlor was only quantified in perch of the site C-25 (0.13 ± 0.02 μg/kg ww). Concentrations of isoproturon were similar for the sites C-45 and C-75 with 0.4 ± 0.1 and 0.75 ± 0.06 μg/kg ww for carp and perch, respectively. Contamination of fish reflected generally concentrations in surroundings. Isoproturon was the most concentrated and its main source was water for perch while carp was exposed through both water and sediments, highlighting their life strategies in pond.

Vertical distribution in soil column and dissipation in soil of benzoylurea insecticides diflubenzuron, flufenoxuron and novaluron and effect on the bacterial community

Benzoylurea insecticides are used for prevention and eradication of household or field pests. However, few studies have investigated their distribution and dissipation in soils and the effects on the soil microbial community. We examined the dissipation and vertical distribution of diflubenzuron, flufenoxuron and novaluron and their effects on bacterial diversity in two soils in Taiwan. The dissipation of the three benzoylureas was concentration dependent. The half-life of 1, 10 and 50 mg kg(-1) concentration was from 3.0 to 45.9, 52.1 to 433.2 and 27.7 to 533.2 d, respectively. The proportion of residual benzoylureas in sterilized soils remained up to 83% at the end of the incubation, which implied that the dissipation was mainly by microorganisms. All three benzoylureas were not detected below 10 cm in soil column experiments. Comparison of initial pesticides concentrations (50 mg kg(-1)), diflubenzuron was detected at <1%. However, flufenoxuron and novaluron remained at >30% and 50% in Pu and Wl soil, respectively after leaching for 70 d. Furthermore, the presence of flufenoxuron and novaluron at 5- to 10-cm depth led to greater change in bacterial community diversity in Pu than Wl soil.

Variation in chlorotoluron photodegradation rates as a result of seasonal changes in the composition of natural waters

BACKGROUND

It is important to understand the degradation of organic molecules in surface waters to ensure that risk assessments, intended to prevent adverse effects on human health and the environment, are robust. One important degradation mechanism in surface waters is photodegradation. This process is generally studied in laboratory test systems, and the significance of the results is then extrapolated to the field. The aim of this work was to assess how fluctuations in the composition of surface water influence the photodegradation rate of chlorotoluron.

RESULTS

Photodegradation DT(50) values in the lake (mean = 26.0 days) and pond (mean = 26.0 days) were significantly slower than in the river (mean = 6.8 days) and stream (mean = 7.3 days) samples. The DT(50) values in the pond and lake samples were similar to the direct photolysis value (mean = 28.6 days). Photodegradation was significantly faster in the stream and river samples, suggesting that indirect photolysis was significant in those waters. Principal component analysis indicated a strong inverse correlation between nitrate concentration and degradation rate.

CONCLUSIONS

Nitrate concentration had a strong influence on the rate of photodegradation, with increasing nitrate concentrations sharply reducing the DT(50) . However, this effect was restricted to a narrow concentration range and levelled off quite quickly, such that further increases in the nitrate concentration had no significant effect on the rate of degradation. Extrapolating photodegradation rates of chlorotoluron from the laboratory to the field should be relatively straightforward, provided the nitrate concentrations in the waters are known.

Mechanistic insights into the role of river sediment in the attenuation of the herbicide isoproturon

Mechanistic insights into the relative contribution of sorption and biodegradation on the removal of the herbicide isoproturon (IPU) are reported. (14)C-radiorespirometry indicated very low levels of catabolic activity in IPU-undosed and IPU-dosed (0.1, 1, 100 μg L(-1)) river water (RW) and groundwater (GW) (mineralisation: <2%). In contrast, levels of catabolic activity in IPU-undosed and IPU-dosed river sediment (RS) were significantly higher (mineralisation: 14.5-36.9%). Levels of IPU catabolic competence showed a positive log-linear relationship (r(2) = 0.768) with IPU concentration present. A threshold IPU concentration of between 0.1 μg L(-1) and 1 μg L(-1) was required to significantly (p < 0.05) increase levels of catabolic activity. Given the EU Drinking Water Directive limit for a single pesticide in drinking water of <0.1 μg L(-1) this result suggests that riverbed sediment infiltration is potentially an appropriate 'natural' means of improving water quality in terms of pesticide levels at concentrations that are in keeping with regulatory limits.

Comparison of greenhouse and field degradation behaviour of isoprocarb, hexaflumuron and difenoconazole in Perilla frutescens

Isoprocarb, hexaflumuron and difenoconazole were used in Perilla frutescens at 600, 60 and 75 g a.i./ha respectively. High performance liquid chromatography-tandem mass spectrometry was used for residue determination because of high selectivity and simple treatment. The results showed that the half-lives of isoprocarb, hexaflumuron and difenoconazole at greenhouse condition were 0.71, 1.63 and 1.21 days respectively, and at field condition, the values were 1.13, 1.07 and 0.92 days respectively.

Toxicology of isoproturon to the food crop wheat as affected by salicylic acid

PURPOSE

Isoproturon, a herbicide belonging to the phenylurea family, is widely used to kill weeds in soils. Recent study indicated that isoproturon has become a contaminant in ecosystems due to its intensive use, thus bringing environmental risks to crop production safety. Salicylic acid (SA) is one of the components in plant defense signaling pathways and regulates diverse physiological responses to biotic and environmental stresses. The purpose of the study is to help to understand how SA mediates the biological process in wheat under isoproturon stress.

METHODS

Wheat seeds (Triticum aestivum, cv. Yangmai 13) were surface-sterilized and placed on moist filter paper for germination. After 24 h, the germinating seeds were placed on a plastic pot (1 L) containing 1,120 g soil mixed with isoproturon at 4 mg kg(-1) soil. After 4 days, wheat leaves were sprayed with 5 mg L(-1) SA. The SA treatment was undertaken once a day and lasted for 6 days, when the third true leaf was well developed. For control seedlings, only water was sprayed. Seedlings were grown under a light intensity of 300 µmol m(-2) s(-1) with a light/dark cycle of 12/12 h at 25°C, and watered to keep 70% relative water content in soils.

RESULTS AND DISCUSSION

We investigated the role of SA in alleviating isoproturon-induced toxicity in the food crop wheat (T. aestivum). Plants exposed to 4 mg kg(-1) isoproturon showed growth stunt and oxidative damage, but concomitant treatment with 5 mg L(-1) SA was able to attenuate the toxic effect. Isoproturon in soils was readily accumulated by wheat, but such accumulation can be blocked significantly by SA application. Treatment with SA decreased the abundance of O(2) (.-) and H(2)O(2), as well as activities of antioxidant enzymes, and increased activities of catalase in isoproturon-exposed plants. The enzyme activities were confirmed by the native polyacrylamide gel electrophoresis. Further, an RT-PCR-based assay was performed to show that several transcripts coding antioxidant enzymes were increased with isoproturon but decreased by SA.

CONCLUSION

The present results indicate that exogenous SA is able to improve the wheat tolerance to isoproturon toxicity.

Assessing the chemical and biological accessibility of the herbicide isoproturon in soil amended with biochar

There is considerable current interest in using biochar (BC) as a soil amendment to sequester carbon to mitigate climate change. However, the implications of adding BC to agricultural soil for the environmental fate of pesticides remain unclear. In particular, the effect of biochars on desorption behavior of compounds is poorly understood. This study examined the influence of BC on pesticide chemical and biological accessibility using the herbicide isoproturon (IPU). Soils amended with 1% and 2% BC showed enhanced sorption, slower desorption, and reduced biodegradation of IPU. Addition of 0.1% BC had no effect on sorption, desorption or biodegradation of IPU. However, the mineralization of (14)C-IPU was reduced by all BC concentrations, reducing by 13.6%, 40.1% and 49.8% at BC concentrations of 0.1%, 1% and 2% respectively. Further, the ratio of the toxic metabolite 4-isopropyl-aniline to intact IPU was substantially reduced by higher BC concentrations. Hydroxypropyl-β-cyclodextrin (HPCD) extractions were used to estimate the IPU bioaccessibility in the BC-amended soil. Significant correlations were found between HPCD-extracted (14)C-IPU and the IPU desorbed (%) (r(2)=0.8518, p<0.01), and also the (14)C-IPU mineralized (%) (r(2)=0.733; p<0.01) for all BC-amended soils. This study clearly demonstrates how desorption in the presence of BC is intimately related to pesticide biodegradation by the indigenous soil microbiota. BC application to agricultural soils can affect the persistence of pesticides as well as the fate of their degradation products. This has important implications for the effectiveness of pesticides as well as the sequestration of contaminants in soils.

Design and development of novel insect growth regulators: synthesis, characterization and effect of benzoyl thymyl thioureas and ureas on total haemocyte count of Dysdercus koenigii

Insect-growth regulators (IGRs) have been receiving foremost attention as potential means of selective insect control. Benzoyl phenyl urea (BPU) is a well-known IGR having chitin synthesis inhibitor activity. Mimics of BPU have been synthesized by suitable derivatization of a naturally occurring monoterpenoid, thymol (2-isopropyl-5-methyl phenol) to form a = series of substituted benzoyl thymyl thioureas (BTTUs) [IVa-f] and benzoyl thymyl ureas (BTUs) [Va-f]. The synthesized compounds have been characterized by (1)H and (13)C NMR, LC-MS and elemental analysis. These derivatives have been screened for their effect on total haemocyte count of Dysdercus koenigii. It has been observed that the introduction of substituted benzoyl thiourea and urea linkage into a thymol ring via an amino group results in higher activity than the parent compound thymol and a comparable pattern of results with the standard insect-growth regulators, Penfluron. Urea [Va-f] compounds exhibited greater effect on Total Haemocyte Count (THC) than thiourea [IVa-f]. Fluoro substitution enhanced the effect on THC more than chloro substituted compounds, while ortho-substitution resulted in a better effect than para-substitution. The results described in this paper are promising and provide new array of synthetic chemicals that may be utilized as insect growth regulators.

[Determination of chlorfluazuron residue in foods by high performance liquid chromatography]

A method for the determination of chlorfluazuron residue in foods by high performance liquid chromatography (HPLC) was developed. The samples were extracted with hexane or acetonitrile. After cleaned up with Florisil-solid phase extraction (SPE), the samples were analyzed by the separation on a C18 chromatographic column with an acetonitrile and water (85 : 15, v/v) mixed solution as the mobile phase and the determination with an ultraviolet detector at 260 nm. The linear range was 0.05 - 2.0 mg/L, the correlation coefficient was 0.999 8 and the limit of quantification (S/N = 10) was 0.05 mg/kg. The recoveries were 82.1% - 102.5% with the relative standard deviations (n = 10) of 3.00% - 6.25% at the three different spiked levels of 0.05, 0.1 and 1 mg/kg. The method is easy, fast, accurate and consuming less sample and organic solvents. It can be applied in the determination of chlorfluazuron in foods.

[Determination of forchlorfenuron and gibberellin acid in the grapes using high performance liquid chromatography-tandem mass spectrometry]

A method was established for the determination of two plant growth regulators, forchlorfenuron (CPPU)and gibberellin acid (GA3), in the grapes using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The sample was extracted with 0.5% (v/v) formic acid aqueous solution and acetonitrile (4: 1, v/v), and cleaned-up with Strata-X solid phase extraction cartridge. The separations were performed on an Agilent SB-C18 column (50 mm x 2.1 mm, 1.8 microm), with a mobile phase of 0.5% formic acid aqueous solution-acetonitrile at a flow rate of 0.3 mL/min and detected by electrospray ionization MS/MS under the multiple reaction monitoring (MRM) mode. The results showed that the good linear relationships and the correlation coefficients greater than 0.999 were obtained. The limits of detection (LODs) were 0.5 microg/L and 0.3 microg/L for CPPU and GA3, respectively. The limits of quantification (LOQs) were 2.0 microg/L and 1.0 microg/L for CPPU and GA3, respectively. The recoveries were 91.7% - 95.6% and 90.3% - 94.2% with the relative standard deviations (RSD) of 4.1% - 7.3% and 3.2% - 6.9% for CPPU and GA3, respectively. The results indicate that the method is accurate and can be used for the determination of CPPU and GA3 residues in the grapes.

High performance liquid chromatography method for residues analysis of thidiazuron in apple and soil

A rapid, sensitive and reliable analytical method for thidiazuron residues in apple and soil was established. The residual levels of the pesticide in apple and soil were determined by high performance liquid chromatography (HPLC) with UV detector. Samples of apple and soil were extracted with acetonitrile-water solutions, and then cleaned up by Florisil or C(18) cartridges. The results showed good linearity (r(2)=1.000) over the concentration range of 0.01-5.0 mg/L. Limits of quantification (LOQ) of the method were 0.01 mg/kg for both soil and apple. Recovery from the apple and soil samples were 83.36%-84.08% and 85.27%-89.83%, respectively, and the corresponding relative standard deviations (RSDs) of the recovery data were 0.155%-0.524% and 0.475%-4.79% for the three fortified levels (0.01, 0.1, 0.5 mg/kg). The analyte in the samples were further confirmed by electrospray ionization tandem mass spectrometry (ESI-MS/MS). It was demonstrated that the proposed method was simple and efficient, and particularly suitable for detecting thidiazuron residues in apple and soil.

Potential use of Lemna minor for the phytoremediation of isoproturon and glyphosate

Pesticides are being detected in water bodies on an increasingly frequent basis. The present study focused on toxicity and phytoremediation potential of aquatic plants to remove phytosanitary products from contaminated water. We investigated the capacity of Lemna minor (L. minor) to eliminate two herbicides isoproturon and glyphosate from their medium. Since phytoremediation relies on healthy plants, pesticide toxicity was evaluated by exposing plants to 5 concentrations (0-20 microg L(-1) for isoproturon and 0-120 microg L(-1) for glyphosate) in culture media for 4 d using growth rate and chlorophyll a fluorescence as endpoints. At exposure concentrations of 10 microg x L(-1) for isoproturon and 80 microg x L(-1) for glyphosate, effects on growth rate and chlorophyll fluorescence were minor (< 25%), so that this initial concentration was selected to study herbicide removal After a 4-d incubation, removal yields were 25% and 8% for isoproturon and glyphosate, respectively.

Selected pesticides adsorption and desorption in substrates from artificial wetland and forest buffer

Buffer zones such as artificial wetlands and forest buffers may help decrease non-point-source pesticide pollution from agricultural catchments. The present study focuses on understanding the role of the substrates mainly found in such buffer zones for pesticide adsorption and desorption. Radiolabeled [(14)C]isoproturon, [(14)C]metazachlor, and [(14)C]epoxiconazole were used to measure adsorption and desorption isotherms on wetland sediments and plants and forest soil and litter from two sites in France. Wetland sediments and forest soil exhibited the most important potential for pesticide adsorption. Wetland plants and forest litter also showed high adsorption coefficients and were associated with highly hysteretic desorption, particularly for the moderately mobile isoproturon and metazachlor. Adsorption of the highly hydrophobic epoxiconazole was strong and associated with weak desorption from all substrates. Calculated sorption coefficients were larger than those classically measured on soils. Isoproturon, metazachlor, and epoxiconazole K(OC) sorption coefficients ranged from 84 to 372, 131 to 255, and 1,356 to 3,939 L/kg, respectively. Therefore, specifically collecting buffer zone substrate sorption data is needed for modeling purposes. Results showed that forests and wetlands present potential for pesticide retention. This may be enhanced by planting vegetation and leaving dead vegetal material in buffer zone design.

Impact of low molecular weight organic acids and dissolved organic matter on sorption and mobility of isoproturon in two soils

Isoproturon is a selective herbicide belonging to the phenylurea family and widely used for pre- and post-emergence control of annual weeds. Soil amendments (e.g. organic compounds or dissolved organic matter) may affect environmental behavior and bioavailability of pesticides. However, whether the physiochemical process of isoproturon in soils is affected by organic amendments and how it is affected in different soil types are unknown. To evaluate the impact of low molecular weight organic acids (LMWOA) and dissolved organic matter (DOM) on sorption/desorption and mobility of isoproturon in soils, comprehensive analyses were performed using two distinct soil types (Eutric gleysols and Hap udic cambisols). Our analysis revealed that adsorption of isoproturon in Eutric gleysols was depressed, and desorption and mobility of isoproturon were promoted in the presence of DOM and LMWOA. However, the opposite result was observed with Hap udic cambisols, suggesting that the soil type affected predominantly the physiochemical process. We also characterized differential components of the soils using three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy and Fourier transform infrared (FT-IR) spectroscopy and show that the two soils displayed different intensity of absorption bands for several functional groups.

Chlorination of chlortoluron: kinetics, pathways and chloroform formation

Chlortoluron chlorination is studied in the pH range of 3-10 at 25 ± 1°C. The chlorination kinetics can be well described by a second-order kinetics model, first-order in chlorine and first-order in chlortoluron. The apparent rate constants were determined and found to be minimum at pH 6, maximum at pH 3 and medium at alkaline conditions. The rate constant of each predominant elementary reactions (i.e., the acid-catalyzed reaction of chlortoluron with HOCl, the reaction of chlortoluron with HOCl and the reaction of chlortoluron with OCl(-)) was calculated as 3.12 (± 0.10)×10(7)M(-2)h(-1), 3.11 (±0.39)×10(2)M(-1)h(-1) and 3.06 (±0.47)×10(3)M(-1)h(-1), respectively. The main chlortoluron chlorination by-products were identified by gas chromatography-mass spectrometry (GC-MS) with purge-and-trap pretreatment, ultra-performance liquid chromatography-electrospray ionization-MS and GC-electron capture detector. Six volatile disinfection by-products were identified including chloroform (CF), dichloroacetonitrile, 1,1-dichloropropanone, 1,1,1-trichloropropanone, dichloronitromethane and trichloronitromethane. Degradation pathways of chlortoluron chlorination were then proposed. High concentrations of CF were generated during chlortoluron chlorination, with maximum CF yield at circumneutral pH range in solution.